This invention relates generally to occupant restraint systems and more particularly to an occupant restraint system having a vent means for venting the deploying cushion to ambient when the pressure within the cushion exceeds a predetermined level.
It is well known to vent deploying occupant restraint cushions to ambient through the use of various types of openings or vents in the cushion. Such vents may be open throughout deployment of the cushion or may be opened only upon the attainment of certain pressure levels within the deploying cushion. The venting of the cushion to ambient reduces the pressure within the deploying cushion to the desired level.
The venting of the cushion in accordance with this invention may be termed force actuated venting since the venting of the deploying cushion to ambient occurs when the reaction force generated by internal cushion pressure resulting from the engagement of the occupant and the deploying cushion exceeds a predetermined level.
In the preferred embodiment of the invention, the cushion, source of pressure fluid, and enclosure for the source and cushion are mounted to a support to provide a module. The support is provided with vent openings therethrough which communicate the interior of the cushion with ambient. These vent openings are of a predetermined size to attain a predetermined vent area. The vent openings are closed by overlying rupturable diaphragms, such as thin glass members mounted to the support around the openings. The module is mounted to the vehicle, such as the hub portion of a vehicle steering wheel, by force collapsible means, such as mesh columns of the type commonly used in energy absorbing steering columns or collapsible cell type material. The vehicle also mounts rupture means, such as rupture pins or struts, having free pointed ends located in aligned relationship to the diaphragms and a predetermined distance therefrom.
When the deploying cushion is engaged by the occupant, the pressure within the cushion normally rises and results in a predetermined reaction force on the support. Should the reaction force on the support exceed a predetermined level, it will start to collapse the force collapsible means. Should the support move through the predetermined distance between the diaphragms and the free ends of the pins or struts, ends of the pins or struts will engage and rupture the diaphragms to vent the deploying cushion to ambient through the support.
Since the reaction force on the support results from the internal pressure of the deploying cushion generated by engagement of the cushion and the occupant, it is a direct measure of the force applied by the cushion to the occupant. By venting the cushion to ambient in accordance with the level of the reaction force, the force applied by the cushion to the occupant can be maintained within predetermined limits. By sizing the openings in the support, setting the force at which the collapsible means collapses, and setting the distance between the diaphragms and the rupture pins or struts, the internal pressure within the deploying cushion and in turn, the force applied by the cushion to the occupant, can be maintained within predetermined limits.
The primary feature of this invention is that it provides an occupant restraint system for venting a deploying cushion to ambient through the support for the deploying cushion in accordance with the reaction force on the support generated by internal cushion pressure resulting from engagement of the deploying cushion with a vehicle occupant. Another feature is that the venting occurs through rupturable vents in the support which communicate the deploying cushion with ambient through the support. A further feature is that the vents are closed by rupturable diaphragms which are ruptured by movement of the support relative to the vehicle when the reaction force on the support exceeds a predetermined limit. Yet another feature is that the support is mounted on the vehicle by force collapsible means and the force collapsible means must collapse a predetermined distance before the diaphragms are ruptured. Yet a further feature is that the rupturable diaphragms engage and are ruptured by rupture pins or struts on the vehicle when the support has moved through the predetermined distance. Still another feature is that the rupturable diaphragms are formed of thin glass members mounted to the support around openings therethrough. Still a further feature is that the cushion, the source of pressure fluid for deploying the cushion, and the enclosure for the cushion and source, are mounted to the support to provide a module which is mounted to the vehicle by columnar type force collapsible means in spaced relationship to the pins or struts of the vehicle. These and other features of this invention will be apparent from the following specification and drawings wherein: